1. Field
The present invention relates generally to a safety release for a shaft drive. More specifically, embodiments of the present invention concern a safety release for use with a powered rotary knife.
2. Discussion of Prior Art
Powered knifes have long been used in the meat processing industry for dressing an animal carcass. The process of dressing the carcass normally involves removing meat and fat from various bones (i.e., boning), cutting various bones, and trimming the meat. Powered rotary knives enable workers to perform this process with much greater efficiency than traditional, unpowered knives. Among these prior art powered knives are rotary knives that include a rotating annular blade rotatably driven within a knife housing. Rotary knives can be either electrically or pneumatically powered and are able to spin the annular blade at very high rotational speeds. Electrically powered rotary knives include an electric motor and a flexible drive shaft that directly connects the motor and the rotary knife (see FIGS. 1 and 2). The prior art flexible drive shaft S depicted in FIGS. 1 and 2 is drivingly connected to the motor M with a quick-coupled connection so that drive shaft S powers rotary knife K.
Conventional rotary knives are problematic and suffer from certain limitations. One problem encountered by prior art knives is that the annular blade within the knife housing can be restricted from rotating during operation. For instance, a bone or other obstruction encountered while dressing a carcass can become lodged between the blade and housing and either slow blade rotation or entirely stop the blade. Also, the annular blade and other components of the rotary knife can become worn from extensive use and cause the blade to bind within the housing. During installation, the annular blade can become misaligned within the housing and blade misalignment can also cause excessive wear of knife components and binding of the blade. Furthermore, the high-speed rotational movement of the annular blade, which is ideal for quickly and efficiently processing meat, often serves to accelerate wear of the annular blade and other knife components and can promote blade binding. The flexible drive shaft of a conventional electrically powered rotary knife can also experience binding (e.g., by becoming kinked or bent) that also restricts rotation of the drive shaft or of the annular blade. For shaft-driven rotary knives, binding of the blade or shaft is known to expose the elongated flexible shaft to a significant amount of torque and cause the flexible shaft to twist or move unexpectedly. Some prior art shaft-driven rotary knives include a lever mounted on the knife handle that can be depressed by the operator to selectively power the knife (e.g., the lever can be released by the operator when an obstruction binds the blade to remove at least some torque on the shaft drive). However, these conventional rotary knives are not ergonomically designed and are known to cause the operator to experience fatigue in the hand and arm from holding the knife and depressing the lever over a long period of time (e.g., a user will operate the same knife for an eight hour work day, five days per week). Accordingly, there is a need for an improved powered rotary knife that does not suffer from these problems and limitations.